Question

I know that when you define a function in vim, you can use the range keyword so that users can say:

:-5,+5call MyFunction()

And then your function gets a:firstline and a:lastline.

What I want is something similar, but more like the traditional vi way of combining a command with a movement, so that ‘d ‘ deletes a space, ‘dw’ deletes a word, ‘d2w’ deletes two words, ‘d2j’ deletes three lines, etc. Assuming my function gets mapped to some input-mode character sequence, is there any way to make it accept similar variable-length inputs, and then modify that text?

Just to be a little more clear, suppose I want to define a function to wrap <b> tags around existing text. We’ll say that function is mapped to ;b. I want users to be able to say ‘;bw’ to bold one word, or ‘;bf.’ to bold everything to the end of the sentence, or whatever, with all the flexibility that vim provides to built-in commands.

Answer 1

If I understand what you’re asking, then all you do is include the char argument in your mapping. For example:

map d :call MyFunction('d')<cr>
map dw :call MyFunction('dw')<cr>
map d2w :call MyFunction('d2w')<cr>
" Of course these would be terrible mappings because they 
" are already mapped to important Vim functions

The way mappings work is that if you “overspecify” a char like ‘d’ above so that it is usable either by itself or as a prefix for longer command, Vim will wait briefly (for timeoutlen)after you press ‘d’ to see if you’re going to press another character. (This depends on thetimeout option being set to true, which is the default.) If you don’t press another character, Vim will execute the ‘d’ mapping. If you do it will call the more complex mapping. See :h map-commands generally and :h map-typing for more.

Note: After your clarification I think what you want is to create a custom ‘operator’ function that you can use to operate on buffer areas defined by Vim motions. See :h map-operator for info on how to do this.